How to make an instance of a model for animation?
You may want to look into blender's concept of NLAs.  Actions are data blocks just like meshes and materials. You can create a new scene with an instance of the armature and mesh.  You can then animate the pose to move the mouth.

You can use the Action Editor mode of the Dope Sheet to figure out the name of the action (and rename it if you like).

Then in your scene you can find your instance of the armature and use the NLA editor to add a track.  Then add a strip to that track and use the mouth animation you created in the other scene.